While extensive progress has been made over the past decade in finding and treating patients with hypertension, it has become increasingly obvious that long term resolution of this problem will require a greater understanding of the basic mechanisms involved so that preventive measures may be taken. Recent studies have suggested that hypertension is the result of flaws in those systems which normally regulate arterial pressure. The overall objective of this proposal is to pursue studies designed to determine the mechanism(s) responsible for the altered adrenal responses to angiotensin II in essential hypertension and their pathophysiologic significance. Clinical studies will be conducted in patients with essential hypertension and parallel studies in two control groups: normotensive subjects and patients with secondary forms of hypertension.